Boletín de aludes

Purcells

Jan 26 – 27, 2012Avalanche Canada
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Archivado · caducó 15 years ago

Peligro de aludes

Sat
Sun
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
2 · Moderado
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Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    2–6
    Watch for wind slab in exposed areas at all three elevation bands as wind continues to redistribute storm snow into soft slabs. Wind exposed slopes need some additional time to settle out before we set our sights on them.

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    4–7
    Two layers to watch: 1. Buried surface hoar, most likely triggered on steep, unsupported slopes amongst the trees. 2. Basal facets, triggerable from thin snowpack areas or by a heavy load (cornice fall, airborne sled). Avalanches could be large.

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–5
    South of Golden, storm snow totals are near 100 cm & a few different shears can be found in the new snow. You're most likely to trigger a storm slab in steep unsupported terrain.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain on Saturday

Weather Forecast

A surface ridge moves into the region Friday keeping the area dry while northwesterly flow aloft keeps scattered clouds in place. Ridgetop winds will be at strong values out of the W near ridgetop Friday & temps will remain cool; Expect a daytime High of -5 and an overnight Low of -12 @ 1500 m. Things begin to change a bit Saturday as the ridge breaks down allowing moist flow in from the pacific. The first storm associated with the new pattern enters the region Saturday night, sticking around through Sunday. Freezing levels are expected to rise to 1300 m Saturday night and storm totals from 20 - 40 cm are forecast at this time.

Avalanche Summary

A couple of large natural avalanches in the alpine (to size 3) were reported on NE and SE- E aspects in the Dogtooth range Wednesday. Smaller avalanches of the loose snow & soft slab variety (to size 1.5) were also reported running in the new/old snow interface. Elsewhere in the region a natural avalanche that started in steep un-skiable terrain was observed. All the reported avalanches were running fast and entraining snow as they ran down the slope.

Snowpack Summary

The Purcell’s are one of the more complex snowpacks in the province right now.Tuesday night/Weds the region received 35 – 60 cm of new snow accompanied by strong winds out of the SW. Just a few days ago the region received 20 – 40 cm with S & SE winds. A test profile on Tuesday revealed a sudden planer shear down 40 cm failing on surface hoar with a hard trigger. That was before the storm, that layer now has 70+ cm of snow on it and is likely more sensitive. Resistant shears were noted in last weekend’s storm snow yesterday too. The bottom line is that there are a number of different weaknesses/sliding layers in the snowpack which are now under additional strain.The mid-December surface hoar/facet persistent weakness, now down around 70cm on the eastern side of the range and as deep as 230cm on the western side, is still causing operators concern, especially in shallow snowpack areas. Recent snowpack tests show moderate to hard, sudden planar results on this layer. The consequences of a failure on this layer would be large. Facets and depth hoar exist at the base of the snowpack. Cornices are large and weak in some areas.

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